1. Field of the Invention
The present invention relates to a vehicle suspension system.
2. Description of the Prior Art
The following arrangement is known as a vehicle suspension system, namely, an upper control arm and two lower control arms arranged in the widthwise direction of a vehicle body are connected with a wheel support member, each of the control arms is supported on a sub-frame connected elastically with the vehicle body and a vertical arm disposed in the longitudinal direction of the vehicle body is connected with the wheel support member to be supported directly by the vehicle body (refer to U.S. Pat. No. 4,671,531).
With the above arrangement, a toe-in replacement is controlled by utilizing the two lower control arms and a camber displacement is controlled by utilizing the upper control arm. Also, it is possible to allot the force in the longitudinal direction of the vehicle body to the vertical arm. Since the vertical arm is supported directly by the vehicle body, the above-mentioned force in the longitudinal direction does not work on the sub-frame and therefore this force does not affect much the control arms, in other words, a good control can be made on wheels.
In the case where a suspension arm, such as the vertical arm mentioned above, is supported on the vehicle body, a main frame extending in the longitudinal direction of the vehicle body and having high rigidity is considered as a supporting position. However, since the main frame is subjected to high load due to its supporting the vertical arm, a special reinforcement is required to receive this load but this raises problems, such as the weight increase of a vehicle.